How does dexamethasone work?

Dexamethasone is a type of medicine known as a corticosteroid. These medicines are man-made versions of the corticosteroid hormones, cortisol and aldosterone, produced naturally by the adrenal glands. They are often simply called steroids, but note they are not the same as anabolic steroids, which are abused by some athletes and body builders.

Corticosteroids have many important functions on every organ system. If the body's natural level of steroid hormones is too low because the adrenal glands are not producing enough hormones, this must be treated with replacement therapy to allow the body to function normally. Dexamethasone is used specifically to treat a disorder of the adrenal glands called congenital adrenal hyperplasia. People with this condition lack an enzyme needed by the adrenal glands to produce cortisol and aldosterone, and without these hormones the adrenal glands produce too many male sex hormones (androgens). This causes early (or inappropriate) appearance of male characteristics. Taking dexamethasone daily helps return the hormone levels to normal.

Corticosteroid hormones are also involved in controlling inflammatory responses in the body. Dexamethasone reduces inflammation by stopping cells from releasing chemicals that normally help produce immune and allergic responses. This can help control a wide number of disease states that involve excessive inflammation, including severe allergic reactions and inflammation of the joints in arthritis.

Dexamethasone also decreases the numbers of white blood cells circulating in the blood and both actions make it useful for treating autoimmune diseases caused by the immune system attacking the body's own tissues, such as many of those listed above. It is also useful for treating certain types of blood cancer where there is excessive production of certain white blood cells.

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